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494 



Journal of the American Mosquito Control Association Vol. 3 No. 3 



THE USED TIRE TRADE: A MECHANISM FOR THE WORLDWIDE 
DISPERSAL OF CONTAINER BREEDING MOSQUITOES 

PAUL REITER 1 and DANIEL SPRENGER 2 

ABSTRACT. Modern transportation methods have facilitated an extensive trade in used tires at the 
national and international level. The history and reasons for this trade are described. Comprehensive 
data on United States imports and United States, Japanese, and Korean exports of used tires for the 
period 1978-85 reveal an unprecedented potential for the worldwide dispersal of important vector 
mosquitoes such as Aedes albopictus and Ae. aegypti. Other articles of commerce with similar potential 
may await recognition. 



INTRODUCTION 

The discovery of an established population of 
Aedes albopictus (Skuse), in Houston, Texas 
(Sprenger and Wuithiranyagool 1986) refocused 
attention on the importance of used tires as a 
breeding site for mosquitoes. During studies of 
this species at a roadside tire dump in Houston, 
we noticed that an apparently worthless tire was 
being removed from the site. On inquiry we 
learned that scavenged tires are sold by at least 
five local companies to buyers in several south- 
ern states and in Mexico, Belize and Guatemala. 
These companies also buy container loads of 
used tires from dealers in other parts of the 
United States and from India, Israel, Japan, 
Korea, the United Kingdom and West Germany. 
Many similar companies operate throughout the 
country. 

Although most medical entomologists were 
unaware of this trade, the United States De- 
partment of Agriculture, the Department of 
Commerce, and the Customs Service confirmed 
that used tires have been a significant national 
and international commodity for nearly two dec- 
ades. Moreover, in the 1960s, during the Aedes 
aegypti Eradication Campaign of the Pan Amer- 
ican Health Organization, Haverfield and Hoff- 
man (1966) demonstrated that used tire ship- 
ments were important in the dispersal of Ae. 
aegypti (L.) in Texas, and suggested that the 
mechanism might also be significant at the in- 
terstate and international level. 

Aedes albopictus is a nonmigratory species 
with a flight range of less than 1 km (Bonnet 
and Worchester 1946, Gubler 1971). The appar- 
ent rapidity of its spread to so many locations 
in the United States [Centers for Disease Con- 
trol (CDC) 1986a, 1986b] is therefore remarka- 
ble, and implies an efficient man-made dispersal 



1 Dengue Branch, Division of Vector-Borne Viral 
Diseases, Center for Infectious Diseases, Centers for 
Disease Control, U. S. Public Health Service, U. S. 
Department of Health and Human Services, G. P. 0. 
Box 4532, San Juan, Puerto Rico 00936. 

2 Harris County Mosquito Control District, 1646 
Old Spanish Trail, Suite 108, Houston, TX 77054. 



mechanism. The used tire trade offers precisely 
such a mechanism. In this paper we describe the 
trade and discuss its potential impact on medical 
entomology. 

HISTORY OF THE USED TIRE 
TRADE 

The importation of mosquito larvae in tires 
was first reported in the mid-1940s, when large 
quantities of war materials ("retrograde car- 
goes") were returned to the United States from 
combat zones. The United States Public Health 
Service (USPHS) found that shiploads of used 
tires arriving from Asian ports after 5 to 7 weeks 
of voyage were heavily infested with up to 7 
species of mosquitoes, including Ae. albopictus 
(Pratt et al. 1946). Strict measures were en- 
forced to eliminate these insects before the car- 
goes were discharged. In a review of this and 
other records of the importation of mosquitoes, 
Hughes and Porter (1956) concluded that used 
tires constitute a ". . . more formidable enemy to 
mosquito control programs than did the old 
sailing vessels with their open water supplies". 

During the period 1966-75, numerous retro- 
grade cargoes of used tires were transported by 
air and sea from southeast Asia to the United 
States by the U. S. government. All shipments 
were routinely treated with mosquito larvicides 
during loading, and inspected in quarantine on 
arrival in the United States. In addition, large 
quantities of used tires from automobiles, 
trucks, aircraft, and earthmoving equipment 
were sold as military surplus in the Republic of 
Vietnam. However, the civilian buyers who 
shipped these tires to the United States were 
not required to treat them with larvicides. 
Among several partial shiploads of such tires 
that were inspected by the USPHS, a small 
infestation of Ae. albopictus was found on one 
occasion (Eads 1972). 

According to trade sources, dealers in the 
United States began importing used tires from 
civilian dealers in other countries at about the 
same time that surplus military tires were being 
sold in Vietnam. Buyers began importing from 
Japan in 1968, but Europe and Canada were the 



September 1987 



Used Tires and Mosquito Dispersal 



495 



3.5t 



~ 3,04 



2.5- 

2.0- 

1.5- 

1.0- 

0.5 

0.0 



LU 



i n ,n.n.n, 



ii 







70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 

YEAR 

Fig. 1. Imports of used tires by the United States, 1970-85. Imports from areas where Aedes albopictus is 
indigenous are shaded. Source: U.S. Department of Commerce, 3 (Adapted from Hawley et al. (1987) with 
permission from Science). 



major sources until the mid 1970s. In 1970, the 
first year for which official trade data are 
available 3 568,862 used tires were imported, of 
which 157,008 (27.6%) were from countries 
where Ae. albopictus is indigenous (Taiwan 61, 
600, Japan 60,794, India 34,614). Used tire im- 
ports from such countries have increased 
greatly, particularly since the end of 1981, while 
imports from other areas, mainly Europe and 
Canada, have remained fairly constant (Fig. 1). 

UTILIZATION OF USED TIRES 

The majority of used tires are traded for reuse 
on vehicles. Differences in legislation and law 
enforcement concerning permissible tire wear, 
the use of recaps, and other criteria mean that 
tires which are not usable in one country are 
often acceptable in others. Enforcement is par- 
ticularly strict in the European Economic Com- 
munity and in Japan. Tires imported from these 
countries are often sold directly to consumers, 
without modification. 

Not all used tires imported by the United 
States are for domestic use. Large quantities are 
exported to other countries, with or without 



3 United States Department of Commerce, Bureau 
of the Census. Imports for consumption, TSUSA cat- 
egory 7725155. Monthly data on microfiche. Also U.S. 
Imports for Consumption and General Imports, 
TSUSA commodity by country of origin, category 
7725155 (pre 1978: category 7257072). Annual data in 
printed form, series FT246 and IM146. 



recapping. In addition, tires for airplanes, earth 
moving equipment, military equipment and 
other special applications are often received for 
repair or recapping and then returned to their 
owners. 
Other options for utilization include: 

1. Whole tires 

a. Recapping 

b. Incineration as fuel 

c. Artificial reefs 

d. Crash barriers, boat fenders 

e. Soil erosion control 

f. Temporary tracks for crawler vehicles 

g. Frost prevention 

2. Chopped/shredded tires 

a. Landfill 

b. Incineration as fuel 

c. Sludge composting 

3. Ground tires 

a. Rubber products, such as porous hosepipe 
for irrigation 

b. Rubberized asphalt 

4. Cut/stamped/dyed tires 

a. Miscellaneous articles, e.g., sandals, floor- 
mats and gaskets 

5. Reclamation of materials 

a. Carbon black 

b. Natural rubber 

The prevalence of these uses varies between 
countries and with time, depending on economic 
factors such as fuel costs and commodity prices. 
National data on utilization are not available 
for the United States, but information for Japan 
is summarized in Fig. 2. In the United States, 



496 



Journal of the American Mosquito Control Association Vol. 3, No. 3 



147c 



12% 




30 7o 



| Discarded 

HI Rubber reclama fion 

Q Retreads 

l-Wil Frost prevention and 
miscellaneous uses 

\Z\ Export 

H Fuel for boilers 



Fuel for metal refining 
and paper manufacture 

Fuel for cement industry 



47. 



Fig. 2. Utilization of used tires in Japan. Source: Japanese Automobile Tire Manufacturer's Association, Inc. 



differences in supply and demand at the local 
level result in a large volume of tire movements 
within the country. Large dealers are usually 
located in highly populated, industrial areas and 
distribute to smaller towns and rural areas. Spe- 
cialists in certain kinds of tires, such as balloon 
tires for swamp vehicles or giant tires for quarry 
equipment, garner their tires from all over the 
country and accumulate stocks to cater to sud- 
den demand. Tires are frequently stored out- 
doors, and marketable stock is often kept adja- 
cent to quasipermanent piles of unusable tires. 
The latter clearly serve as reservoirs for mos- 
quitoes, facilitating rapid infestation of new 
stock as it arrives. 

IMPORT/EXPORT DATA 

United States. In the period 1978-85, the 
United States imported 3 11.6 million used tires 
from 58 countries (Table 1), 7.6 million of which 
were from 13 countries where Ae. albo- 
pictus is indigenous. In the same period, the 
United States exported 4 over 6.3 million used 
tires to more than 60 countries (Table 2). Im- 
ports under "Free Trade Zone" regulations, for 
re-export, are not included in these data, but are 
also considerable. For example, a dealer inter- 
viewed in Houston had just arranged a shipment 
of 300,000 used truck tires from Bordeaux, 
France to Shanghai, China, via New York and 
Houston. Such shipments often involve sorting, 



grading and recapping at locations in the United 
States before export. 

According to the U. S. Department of Com- 
merce, Taiwan is the largest exporter of used 
tires to the United States but informants in the 
trade deny that this is true. Some sources have 
suggested that shipments from Taiwan and 
Hong Kong are augmented by transhipments 
from other countries in order to exploit favora- 
ble trade tariffs 5 . 

Japan. Japanese imports of used tires are 
relatively small 6 but in the period 1978-85, Ja- 
pan exported 15.6 million used tires 7 to more 
than 80 countries (Table 3). Japan had a larger 
share (2.4 million) of the total used tire market 
in the Caribbean and Central and South Amer- 
ica than the United States (1.7 million). Many 
countries bought from both countries, but one 
of the two was usually dominant. For example, 
Japan had 91.8% of the market in the Domini- 
can Republic and 99.6% in Haiti, whereas the 
United States had 99.6% in Mexico and 100% 
in Venezuela. 

Other countries. The Republic of Korea is the 
only other Asian country for which we have been 



4 United States Department of Commerce, Bureau 
of the Census. U. S. Exports, Schedule E, commodity 
by country, TSUSA categories 7725160, 6257027, 
6257070, 6257072 and 6257074, depending on year. 
Annual data in printed form, series FT446 and EM546 
(through 1979), series FT410 (1980 and after). 



5 At the time of printing, the U. S. Department of 
Commerce have informed us that there are serious 
errors in their published data on imports of used tires 
from Taiwan for 1985 and 1986. Apparently this is the 
result of an error in the classification of data supplied 
by the U. S. Customs authorities. We have no infor- 
mation on the accuracy of data for Taiwan in previous 
years. 

6 United Nations Statistical Office, New York 
Branch, "COMTRADE" database, category No. 
625.99, computer database SITC Rev. 2. 

7 Japanese Tariff Association. Japanese exports and 
imports. Exports of commodity by country. Category 
40-11-510. Monthly data in printed form. 



September 1987 



Used Tires and Mosquito Dispersal 



497 



Table 1. Imports of used tires by the United States, 1978-85. (Source: U. S. Department of Commerce, 

Bureau of the Census 3 ). 



Country 


Total 


Country 


Total 




AMERICAS 




ASIA 






Brazil 


5,736 


China 


14 




Canada 


1,644,831 


Hong Kong 


296,792 




Colombia 


15 


India 


23,304 




Dominican Republic 


447 


Indonesia 


1,231 




Jamaica 


488 


Israel 


66,058 




Mexico 


347,646 


Japan 


3,437,811 




Netherlands Antilles 


637 


Malaysia 


728 




Peru 


16,897 


Oman 


523 




Suriname 


9,971 


Pakistan 


53 




Trinidad 


110,006 


Philippines 


1,530 




Uruguay 


204 


Republic of Korea 


141,449 




Venezuela 


408 


Saudi Arabia 
Singapore 


264 
834 




TOTAL 


2,137,286 


Sri Lanka 
Taiwan 


792 
3,693,791 




EUROPE 




Thailand 


1 




Austria 


945 


Turkey 


6 




Belgium 


81,708 








Bulgaria 


123 


TOTAL 


7,665,181 




Czechoslovakia 


4,540 








Denmark 


1,375 


AFRICA 






Federal Republic of Germany 


244,731 


Niger 


304 




Finland 


1,312 


South Africa 


16 




France 


91,311 








German Democratic Republic 


5,143 


TOTAL 


320 




Greece 


381 








Hungary 


11,606 


PACIFIC 






Ireland 


13,984 


Australia 


2 




Italy 


41,010 


French Polynesia 


12 




Netherlands 


223,404 


New Zealand 


2,973 




Norway 


341 








Poland 


8,192 


TOTAL 


2,987 




Portugal 


8,081 








Romania 


578 


WORLD TOTAL 


11,590,921 




Spain 


7,481 








Sweden 


40,266 








Switzerland 


2,430 








United Kingdom 


908,542 








U.S.S.R. 


457 








Yugoslavia 


87,206 








TOTAL 


1,785,147 









able to obtain export information (Table 4). 
Korean exports of used tires are reported to the 
United Nations under category SITC 625.99, 
which is mainly composed of used tires but 
includes some other items such as new tires for 
artillery weapons and baby carriages. In the 
period 1978-84, Korea reported 16.6 thousand 
metric tons of exports under this category (tires 
for road vehicles are 100-300 per metric ton). 

SIGNIFICANCE OF MODERN 
TRANSPORTATION METHODS 

In the past two decades, a revolution in cargo 
handling methods has had more effect on marine 



transportation than any event since the transi- 
tion from sail to steam. Containerization, fast 
container vessels, computerization, and satellite 
communications have greatly reduced the time 
it takes to load, ship, and deliver cargoes. Esca- 
lating trade volume, short transit times, and 
favorable environmental conditions inside con- 
tainers have also greatly increased the number 
of insect-infested cargos intercepted at ports in 
the United States (Fig. 3). 

Reiter and Darsie (1984) pointed out that 
these changes constitute a quantum leap in the 
potential mobility of arthropod vectors. Their 
study was prompted by the appearance of a 
single specimen of Ae. albopictus in Memphis, 



498 



Journal of the American Mosquito Control Association Vol. 3, No. 3 



Table 2. Exports of used tires by the United States, 1978-85. (Source: U.S. Department of Commerce, Bureau 

of the Census 4 ). 



Country 


Total 


Country 


Total 




AMERICAS 




PACIFIC 






Argentina 


6,123 


Australia 


36,739 




Bahamas 


2,416 


New Zealand 


3,099 




Bolivia 


548 


Papua New Guinea 


1,182 




Brazil 


8,256 








Canada 


3,520,457 


TOTAL 


41,020 




Chile 


4,857 








Colombia 


14,989 


ASIA 






Costa Rica 


7,970 


Hong Kong 


18,000 




Dominican Republic 


148,294 


Indonesia 


356 




Ecuador 


9,933 


Iran 


868 




El Salvador 


3,335 


Iraq 


100 




Guatemala 


11,338 


Israel 


19,569 




Guyana 


3,530 


Japan 


26,914 




Haiti 


806 


Jordan 


4,805 




Honduras 


45,499 


Kuwait 


11,655 




Jamaica 


16,357 


Lebanon 


909 




Leeward Islands 


4,518 


Qatar 


1,590 




Mexico 


839,828 


Republic of Korea 


400 




Netherlands Antilles 


33,200 


Saudi Arabia 


264,669 




Nicaragua 


46,007 


Singapore 


518 




Panama 


33,559 


Thailand 


555 




Peru 


10,163 


United Arab Emirates 


2,556 




Trinidad and Tobago 


45,672 








Venezuela 


383,520 


TOTAL 


353,464 




TOTAL 


5,201,175 


AFRICA 
Egypt 


3,385 




EUROPE 




Libya 


625 




Austria 


556 


Morocco 


340 




Belgium 


13,120 


Nigeria 


8,408 




Denmark 


42,467 


South Africa 


26,219 




Federal Republic of Germany 


93,886 


Senegal 


603 




France 


63,811 








Greece 


4,060 


TOTAL 


39,580 




Iceland 


12,007 








Italy 


82,031 


Not Specified 


216,823 




Netherlands 


20,526 








Norway 


1,015 


WORLD TOTAL 


6,343,856 




Spain 


905 








Sweden 


18,538 








Switzerland 


3,903 








United Kingdom 


134,969 








TOTAL 


491,794 









Tennessee. They were unaware of the existence 
of the worldwide trade in used tires and specu- 
lated that this mosquito had travelled as an 
adult in a container delivered to the area. They 
also failed to realize that containerization has 
facilitated commerce in many items that were 
simply impractical to transport by previous 
methods. Used tires are a good example: because 
they are an awkward, bulky item, they were once 
very costly to handle, particularly at the dock- 
side. By contrast, they now move directly from 
seller to buyer in containers, and importers 



range from large, national companies importing 
thousands of container loads per year to small 
businesses that make occasional orders for a 
single container. 

PORT INSPECTION 

In the United States, imported goods are not 
inspected for insects of medical importance, al- 
though selected cargoes are inspected for agri- 
cultural and veterinary pests. Tires are routinely 
checked by the U. S. Customs Service, and must 



September 1987 



Used Tires and Mosquito Dispersal 



499 



Table 3. Japanese exports of used tires, 1978-86. (Source: Japanese Tariff Association 7 ). 



Country 


Total 


Country 


Total 


AMERICAS 




ASIA 




Belize 


1,966 


Afghanistan 


19,109 


Brazil 


3,267 


Bahrain 


244 


Canada 


292,680 


Bangladesh 


3,533 


Cayman Islands 


2,615 


China 


1,064,345 


Chile 


6,462 


Hong Kong 


3,889,034 


Cuba 


1,099 


Indonesia 


738 


Dominican Republic 


1,660,033 


Iran 


136 


Dominica 


41,292 


Iraq 


6,662 


El Salvador 


10,203 


Jordan 


12,724 


Guatemala 


3,880 


Lebanon 


53 


Haiti 


192,278 


Macao 


728 


Honduras 


10,191 


Malaysia 


13,500 


Jamaica 


2,610 


North Korea 


5,950 


Mexico 


3,336 


Oman 


400 


Netherlands Antilles 


282 


Pakistan 


2,229,664 


Panama 


88,735 


Philippines 


886,824 


Paraguay 


10 


Qatar 


210 


Puerto Rico 


12,526 


Republic of Korea 


1,320 


St. Lucia 


490 


Saudi Arabia 


122 


St. Pierre/Miquelon 


296 


Singapore 


70,335 


Suriname 


3,538 


Sri Lanka 


226,659 


Trinidad and Tobago 


31,782 


Taiwan 


4,511 


United States 


2,911,606 


Thailand 


4,158 


U. S. Virgin Islands 


710 


United Arab Republics 


2,309 






Vietnam 


76,109 


TOTAL 


5,281,887 


Yemen 


50 


EUROPE 








Belgium 


2,234 


TOTAL 


8,519,427 


Cyprus 


3,495 






Federal Republic of Germany 


25,142 


AFRICA 




Finland 


609 


Algeria 


40 


France 


35 


Botswana 


1,104 


Iceland 


1,759 


Cameroon 


1,060 


Italy 


20 


Kenya 


1,900 


Netherlands 


10,672 


Mauritius 


1,882 


Poland 


1,070 


Morocco 


510 


Portugal 


585 


Nigeria 


42 


United Kingdom 


23,385 


Senegal 


792 






Somalia 


10 


TOTAL 


69,006 


South Africa 


1,065,211 






Swaziland 


491 


PACIFIC 




Tanzania 


912 


Australia 
Fiji 


640,724 
10,310 


Togo 
Zambia 


3,890 

12 


Guam 


69 






Mariana/Caroline Islands 


8,933 


TOTAL 


1,077,892 


New Zealand 


1,000 






Papua New Guinea 
Samoa 


300 
100 


WORLD TOTAL 


15,610,913 


Tonga 


965 






Western Samoa 


300 






TOTAL 


662,701 







be steam cleaned under the supervision of the 
U. S. Department of Agriculture if they are 
contaminated with earth, to avoid the importa- 
tion of animal viruses and plant nematodes. 



However, there is no requirement to search for 
water or mosquitoes, nor even to record if they 
happen to be present. The time and labor re- 
quired to unload, inspect, and repack containers 



500 



Journal of the American Mosquito Control Association Vol. 3, No. 3 



Table 4. Exports of used tires (metric tons) by South Korea to a selection of countries, 1978-84 (Source- 

United Nations Statistical Office 6 ). 



Country 


Total 


Country 


Total 


AMERICAS 




AFRICA 




Antigua/Barbuda 


6 


Angola 


1,507 


Barbados 


43 


Benin 


32 


Bolivia 


1,160 


Burundi 


118 


Chile 


2,071 


Cameroon 


56 


Colombia 


1,944 


Djibouti 


68 


Costa Rica 


552 


Egypt 


3,837 


Dominican Republic 


1,101 


Ethiopia 


943 


Dominica 


1,323 


Ghana 


3,449 


Ecuador 


1,777 


Ivory Coast 


488 


El Salvador 


203 


Kenya 


1,139 


Guatemala 


144 


Liberia 


527 


Guyana 


14 


Libya 


2,123 


Haiti 


257 


Malawi 


392 


Honduras 


3,325 


Mozambique 


82 


Mexico 


5,178 


Nigeria 


2,377 


Netherlands Antilles 


248 


Sierra Leone 


709 


Nicaragua 


657 


Somalia 


979 


Panama 


3,103 


South Africa 


74 


Paraguay 


107 


Sudan 


1,152 


Peru 


180 


Tanzania 


333 


Suriname 


490 


Togo 


15 


Trinidad & Tobago 


215 


Tunisia 


1 


United States 


167,855 


Uganda 


36 


Uruguay 


373 






Venezuela 


9,678 


TOTAL 


20,437 


TOTAL 


202,004 


PACIFIC 








Australia 


16,419 


MEDITERRANEAN 




New Zealand 


174 


France 


169 






Greece 


503 


TOTAL 


16,593 


Italy 


1,226 






Portugal 


44 


WORLD TOTAL 


253,203 


Spain 


139 






Turkey 


12,088 






TOTAL 


14,169 







2 35 



uj 20 



o I 

° 5 

UJ 

<n 




£ 1978 1979 1980 1981 1982 1983 



2 YEAR 

Fig. 3. Insect-infested cargoes intercepted by the 
United States Department of Agriculture, 1978-83. 
Source: USDA APHIS PPQ List of intercepted plant 
pests. Printed annually or biannually. 



of used tires preclude routine cleaning of these 
cargoes by the Department of Agriculture. 



CONCLUSION 

At the time of writing, infestations of Ae. 
albopictus have been found in twelve states in 
the United States and four in Brazil (CDC 
1986a, 1986b). Nearly all infestations have been 
in tires, although this probably reflects bias in 
search procedure. In late 1986, larvae of Ae. 
albopictus and four other mosquito species were 
found in two container loads of used tires in- 
spected in the Port of Seattle, Washington, less 
than three weeks after they were shipped from 
Asia (CDC 1986b and unpublished information). 



September 1987 



Used Tires and Mosquito Dispersal 



501 



Larvae of Ae. albopictus have also been found in 
newly imported used tires in Barbados, West 
Indies (PAHO/WHO, unpublished informa- 
tion). There is little reason to doubt, therefore, 
that the used tire trade has been a major factor 
in the establishment and dispersal of Ae. albo- 
pictus in the western hemisphere. 

Several points emerge from this conclusion: 

(1) There is no reason to suppose that Ae. 
albopictus is the only container breeding mos- 
quito to have become established after introduc- 
tion in used tires. The species is conspicuous 
and easy to identify, yet its widespread distri- 
bution in the United States was only recognized 
after the Houston infestation was made public. 
Other, less readily identifiable species may also 
have become established and simply await de- 
tection. 

(2) Used tires are a well -recognized mosquito 
breeding site, but other items of modern com- 
merce can serve the same purpose. Examples 
include the large quantities of iron buckets, 
bowls and other water- holding containers which 
are exported from Asia to many countries in 
Africa and Asia, used construction machinery 
which is sold to buyers around the world, and 
cut orchids which are packed in wet wood shav- 
ings and shipped from southeast Asia to many 
countries in Europe and the Americas. 

(3) Because the container trade is an inter- 
national phenomenon, all countries face the risk 
of importation of vector species. The reintro- 
duction of Ae. aegypti into Europe or Anopheles 
gambiae Giles into South America are examples 
of introductions which could have serious public 
health consequences. 

We believe that these circumstances merit 
urgent discussion at the international level. 



ACKNOWLEDGMENTS 

We are grateful to Dr. D. J. Gubler and Dr. 
G. G. Clark for useful comments on the manu- 
script. 

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